This invention relates to the recovery of hexabromocyclododecane product, usable as flame retardant. In one aspect, this invention relates to methods for the recovery of a hexabromocyclododecane product having preferred ratios of isomers.
Bromination of cyclododecatriene produces hexabromocyclododecane isomers having differing melting points. The melting point characteristics of hexabromocyclododecane product obtained from these compositions are known to be related, in part, upon the ratios and distributions of hexabromocyclododecane isomers within the product. For instance, see U.K. Pat. Appl. 2,205,830 and Jap. Pat. Publ. (Kokoku) 50-5187. However, methods to provide an adjustment in the ratio of isomers to affect melting point characteristics are not taught and there continues to be a need for such methods.
The forming of an HBCD reaction mass by admixing bromine and cyclododecatriene in a solvent system comprising alcohol and halogenated hydrocarbon is illustrated in the following patents, incorporated in their entirety herein by reference:
U.S. Pat. No. 3,558,727 (Jenkner et al) PA1 U.S. Pat. No. 3,652,688 (Olechowski et al) PA1 U.S. Pat. No. 3,833,675 (Newcombe et al) PA1 U.K. 2,205,830 (Hermolin et al) PA1 D.E. 3,120,621 (Jenkner et al)
As illustrated in these patents, bromine and cyclododecatriene can be admixed in approximately stoichiometric amounts, optionally with a slight excess of bromine, e.g. about 3 to about 5 percent excess bromine, so as to permit bromination of the cyclododecatriene to form HBCD. This bromination occurs in a solvent system to effect the formation of the HBCD product. The final HBCD product formed by this reaction will typically comprise HBCD in solid particle form, these particle forms being tainted or contaminated with residual bromides (e.g. water soluble bromides such as halogen bromides) as well as unreacted or partially reacted cyclododecatriene (e.g. tetrabromocyclododecadene). The solvents of the solvent system can also react with one or more of the reactants to form possible contaminants, such as reaction with bromine to form alkyl bromides (e.g. isobutyl bromide when isobutyl alcohol is the alcohol in the solvent system). The method of admixing the reactants together with the solvent system can be varied, as illustrated in these patents, including as spacial introduction of the reactants apart from each other or the recycling of recovered mother liquor from downstream separation processes. Admixing can involve agitation of some sort so as to provide a more homogeneous reaction environment. The bromination of cyclododecatriene is an exothermic reaction which preferably can be controlled by cooling of the reaction mass to below about 70.degree.. The prior art heretofore has shown a preference to cool to below 40.degree. C.